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}, { "occurredTime": "1961-04-18T00:00:00Z", "stage": 10.37, "flow": 73200, "preliminary": "O", "olddatum": true }, { "occurredTime": "1961-04-14T00:00:00Z", "stage": 11.71, "flow": 92600, "preliminary": "O", "olddatum": true }, { "occurredTime": "1961-02-27T00:00:00Z", "stage": 12.23, "flow": 101000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1961-02-21T00:00:00Z", "stage": 13.15, "flow": 116000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1960-05-10T00:00:00Z", "stage": 13.66, "flow": 124000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1960-04-06T00:00:00Z", "stage": 13.35, "flow": 119000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1960-04-01T00:00:00Z", "stage": 12.29, "flow": 102000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1958-05-07T00:00:00Z", "stage": 12.02, "flow": 82100, "preliminary": "O", "olddatum": true }, { "occurredTime": "1958-03-29T00:00:00Z", "stage": 11.19, "flow": 67200, "preliminary": "O", "olddatum": true }, { "occurredTime": "1958-03-01T00:00:00Z", "stage": 10.18, "flow": 49000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1957-04-07T00:00:00Z", "stage": 11.4, "flow": 78600, "preliminary": "O", "olddatum": true }, { "occurredTime": "1957-02-12T00:00:00Z", "stage": 11.1, "flow": 74300, "preliminary": "O", "olddatum": true }, { "occurredTime": "1956-07-21T00:00:00Z", "stage": 10.75, "flow": 72500, "preliminary": "O", "olddatum": true }, { "occurredTime": "1955-08-20T00:00:00Z", "stage": 17.6, "flow": 216000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1955-03-23T00:00:00Z", "stage": 11.47, "flow": 99500, "preliminary": "O", "olddatum": true }, { "occurredTime": "1954-10-17T00:00:00Z", "stage": 13.3, "flow": 131000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1954-04-09T00:00:00Z", "stage": 10.46, "flow": 68600, "preliminary": "O", "olddatum": true }, { "occurredTime": "1954-03-03T00:00:00Z", "stage": 12.47, "flow": 116000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1953-03-26T00:00:00Z", "stage": 11.44, "flow": 99100, "preliminary": "O", "olddatum": true }, { "occurredTime": "1952-11-23T00:00:00Z", "stage": 13.76, "flow": 140000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1952-06-15T00:00:00Z", "stage": 12.09, "flow": 110000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1952-04-29T00:00:00Z", "stage": 14.17, "flow": 148000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1952-03-13T00:00:00Z", "stage": 11.95, "flow": 108000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1950-12-09T00:00:00Z", "stage": 12.48, "flow": 117000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1950-12-06T00:00:00Z", "stage": 13.85, "flow": 140000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1949-07-19T00:00:00Z", "stage": 10.26, "flow": 91300, "preliminary": "O", "olddatum": true }, { "occurredTime": "1949-06-20T00:00:00Z", "stage": 13, "flow": 135000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1948-04-16T00:00:00Z", "stage": 10.69, "flow": 97300, "preliminary": "O", "olddatum": true }, { "occurredTime": "1948-02-16T00:00:00Z", "stage": 10.69, "flow": 75000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1945-09-20T00:00:00Z", "stage": 13.88, "flow": 138000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1942-12-31T00:00:00Z", "stage": 13.15, "flow": 139000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1942-10-17T05:45:00Z", "stage": 26.88, "flow": 447000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1942-05-24T00:00:00Z", "stage": 13.17, "flow": 139000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1940-04-22T00:00:00Z", "stage": 11.29, "flow": 107000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1939-02-05T00:00:00Z", "stage": 12.6, "flow": 129000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1937-10-30T00:00:00Z", "stage": 15.62, "flow": 181000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1937-08-27T00:00:00Z", "stage": 10.1, "flow": 88300, "preliminary": "O", "olddatum": true }, { "occurredTime": "1937-04-28T00:00:00Z", "stage": 23.3, "flow": 347000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1937-02-23T00:00:00Z", "stage": 10.58, "flow": 96000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1937-01-24T00:00:00Z", "stage": 10.5, "flow": 94400, "preliminary": "O", "olddatum": true }, { "occurredTime": "1936-03-19T16:45:00Z", "stage": 28.1, "flow": 484000, "preliminary": "R", "olddatum": true }, { "occurredTime": "1936-03-13T00:00:00Z", "stage": 11.16, "flow": 106000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1936-02-27T00:00:00Z", "stage": 14.69, "flow": 132000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1936-02-17T00:00:00Z", "stage": 10.37, "flow": 45000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1934-12-02T00:00:00Z", "stage": 13.5, "flow": 139000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1933-08-25T00:00:00Z", "stage": 10.57, "flow": 92700, "preliminary": "O", "olddatum": true }, { "occurredTime": "1933-04-22T00:00:00Z", "stage": 12.8, "flow": 127000, "preliminary": "O", "olddatum": true }, { "occurredTime": "1933-04-19T00:00:00Z", "stage": 10.15, "flow": 86700, "preliminary": "O", "olddatum": true }, { "occurredTime": "1932-05-14T00:00:00Z", "stage": 15.25, "flow": 168000, "preliminary": "O", "olddatum": true } ] }, "lowWaters": { "historic": [] }, "impacts": [ { "stage": 17, "statement": "Water overflows the overlooks at Great Falls National Park and approaches the lower level of the visitors center. Most of the C&O Canal towpath downstream of Pennyfield is flooded. There is approximately a foot of water in the clubhouse on Sycamore Island." }, { "stage": 16, "statement": "Water reaches the clubhouse on Sycamore Island." }, { "stage": 15, "statement": "Most of the C&O Canal towpath from Pennyfield downstream is flooded." }, { "stage": 14, "statement": "Significant portions of the C&O Canal towpath are flooded. The Blockhouse Point Park is flooded. Water reaches the retaining wall at Overlook 1 at Great Falls National Park but does not overtop it." }, { "stage": 12, "statement": "The C&O Canal overflows at the Great Falls Tavern. Water covers the towpath in many areas." }, { "stage": 11.5, "statement": "Water covers the towpath in multiple spots between the Washington Aqueduct Dam and Pennyfield Lock, mileposts 15 to 19 on the C&O Canal." }, { "stage": 11, "statement": "Water covers the towpath between Swains Lock and Pennyfield Lock, mileposts 17 to 19 on the C&O Canal." }, { "stage": 10, "statement": "Water begins to overflow the banks into low lying areas on the Maryland side of the river near Little Falls. Water begins to enter the canoe shed at Sycamore Island." }, { "stage": 9, "statement": "Several trails on both sides of the river between Great Falls and the Chain Bridge are flooded and will be closed." }, { "stage": 7, "statement": "Upper portions of the River Trail at Great Falls National Park begin to flood and will be closed." }, { "stage": 5.5, "statement": "Water reaches the top of the ferry landing for Sycamore Island. Ferry service to the island will likely be suspended." }, { "stage": 5, "statement": "Portions of the Potomac Heritage Trail begin to flood. Water begins to affect portions of the Billy Goat Trail between Great Falls and Carderock. These trails will be closed. " }, { "stage": 4.5, "statement": "The river reaches danger level for boaters, as defined by the State of Maryland. Conditions for boating will be extremely hazardous." }, { "stage": 3.5, "statement": "The river reaches caution level for boaters, as defined by the State of Maryland. Fast moving water and changing currents will be experienced." } ] }, "images": { "probability": { "weekint": { "stage": "https://water.noaa.gov/resources/probabilistic/exceedance/BRKM2.SSTG.prob.weekint.gif", "flow": "https://water.noaa.gov/resources/probabilistic/exceedance/BRKM2.QINE.prob.weekint.gif", "volume": "https://water.noaa.gov/resources/probabilistic/exceedance/BRKM2.volume.prob.weekint.gif" }, "entperiod": { "stage": "https://water.noaa.gov/resources/probabilistic/exceedance/BRKM2.SSTG.exceed.90day.gif", "flow": "https://water.noaa.gov/resources/probabilistic/exceedance/BRKM2.QINE.exceed.90day.gif", "volume": "" }, "shortrange": "https://water.noaa.gov/resources/probabilistic/short_term/BRKM2.shortrange.hefs.png" }, "hydrograph": { "default": "https://water.noaa.gov/resources/hydrographs/brkm2_hg.png", "floodcat": "https://water.noaa.gov/resources/hydrographs/brkm2_record.png" }, "photos": [] }, "dataAttribution": [ { "abbrev": "US Geological Survey", "text": "USGS--Water Resources of the United States", "title": "US Geological Survey", "url": "https://waterdata.usgs.gov/nwis" }, { "abbrev": "USGS", "text": "01646500", "title": "Observations courtesy of U.S. Geological Survey", "url": "https://waterdata.usgs.gov/nwis/inventory/?site_no=01646500" } ], "impactsLowWaters": [], "normalThreshold": { "value": 0, "units": "ft" }, "hydronotes": [ { "statement": "Stage may be affected by ice.", "effective": "1201", "expiration": "0315" } ], "datums": { "vertical": { "value": [ { "label": "North American Vertical Datum of 1988", "abbrev": "NAVD88", "description": "A fixed reference for elevations determined by geodetic leveling. The datum was derived from a general adjustment of the first-order terrestrial leveling nets of the United States, Canada, and Mexico. In the adjustment, only the height of the primary tidal bench mark, referenced to the International Great Lakes Datum of 1985 (IGLD 85) local mean sea level height value, at Father Point, Rimouski, Quebec, Canada was held fixed, thus providing minimum constraint. NAVD 88 and IGLD 85 are identical. However, NAVD 88 bench mark values are given in Helmert orthometric height units while IGLD 85 values are in dynamic heights. See International Great Lakes Datum of 1985, National Geodetic Vertical Datum of 1929, and geopotential difference. NAVD 88 should not be used as Mean Sea Level.", "value": 37.2 } ] }, "horizontal": { "value": [] }, "notes": { "value": [] } }, "inundation": { "enabled": false, "url": "", "zeroDatum": null, "downloads": null, "siteSpecificInfo": "", "dataAttribution": [] }, "upstreamLid": "EDFM2", "downstreamLid": "GTND2", "inService": { "enabled": true, "message": "" }, "lowThreshold": null, "forecastReliability": "Forecasts are issued routinely year-round.", "TruncateObs": "-1", "TruncateFcst": "-1", "ObservedFloodCategory": "no_flooding", "ForecastFloodCategory": "no_flooding" }